Conversion of hydrocarbon gases



NW 7, 1933. G. EGLOFF 1,933,345

CONVERSION OF HYDROCARBON GA SES Filed July 12, 1929 Patented Nov. 7, 1933 OFFICE 1,933,845 CONVERSION OF HYDROCABBON GASES Gustav Eglofl, Chicago, 111., assignor to Universal il Products Company,

Chicago, 11]., a corporation of South Dakota Application July 12, 1929. Serial No. 377,675

3 Claims.

This invention relates to improvements in the treatment of hydrocarbon gas for the production therefrom, by conversion, of liquid hydrocarbons of the aromatic series. More particularly, it relates to the cracking. of either natural, cracked,

by-product coke oven gas, or similar hydrocarbon gas from any source, including petroleum still gases, illuminating gas from the cracking of gas oil and the like, under controlled conditions of high temperature and pressure sufficient to convert same into benzol and allied liquids containing a high percentage of aromatic compounds.

In one specific embodiment of my invention, I pass the hydrocarbon gas through a heater at high temperature and pressure, and, by regulation of the pressure relative to the particular gas being treated, I am able to convert a substantial portion of the gas into liquefiable products of the aromatic series.

The pressure required for the process of my invention may vary from sub-atmospheric to superatmospheric, the choice of the pressure condition being dependent upon the nature of the gas being treated and the products desired. For 95 instance, by-product coke oven gas already contain's'a relatively large amount of compounds of the aromatic series; nevertheless, it contains very little liquefiable constituents since these are already removed in the scrubbing process before 39 the gas is discharged from the by-product coking operation. Since the compounds of the aromatic series in by-product coke oven gas are more resistant to molecular change by thermal means, usually a pressure of at least 100 pounds to the square inch and a temperature of approximately 1400 to 1600 F. will be required to convert the aromatic compounds in by-product coke oven gas into liquefiable products of the aromatic series. Some of the more easily decomposed gases from 0 other sources, such, for instance, as cracked gas or natural gas, will crack at a lower temperature, for instance, from 1000" F. to 1200 F. In the latter case it may not be desirable to employ superatmospheric pressure at all; under certain 5 conditions, even slight vacuum will give improved results.

It is to be understood that in its broad concept the invention contemplates the subjection of hydrocarbon gas from any source to controlled 0 conditions of high temperature and pressure for the purpose of converting a substantial portion of the gas into liquefiable products of the aromatic series. The invention is not to be limited to any particular hydrocarbon gas.

5 It will be apparent that, at the high temperatures indicated, the chemical reaction is rapid and the nature and the amount of liquefiable constituents produced by the cracking reaction will depend, to a large extent, upon close regulation of the time during which the gas is subjected to 00 the high temperature condition. I have found it desirable, therefor to control the temperature at the outlet of the heating element within very close limits and to cool the products of reaction quickly by means of an absorbing or cooling medium, which will retard excess conversion. This absorbing or cooling medium may be introduced into direct physical contact with the heated products of reaction, in which event it will assist in extracting the condensible constituents produced by the cracking reaction, or if desired, the absorbing or cooling medium may be introduced into indirect contact with the products of reaction. In either event it will be understood that the amount and temperature of the cooling medium used in checking excess conversion will be so controlled as to bring about the desired checking without interfering with the efiiciency of the cracking reaction.

After cooling to a temperature below that at which excess reaction will continue, the partially cooled material is delivered to a stabilizer, or the like, where a close separation is eflected be tween the gas and the absorbing medium in which will be contained the liquefiable hydrocarbons produced by the cracking reaction. Where the cooling medium has not been introduced into direct contact with the heated products of reaction, the latter will also be preferably introduced to a stabilizing tower where separation takes place between the fixed gas and condensible hydrocarbons.

It has been found that from .5 to 3 gallons of liquefiable hydrocarbons per thousand cubic feet of hydrocarbon gas may be obtained by the operationof my process depending, to a large extent, on the source and character of the gas being processed and the temperature and pressure conditions used.

Many other advantages and objects of the in- 109 vention will be more apparent from the following description.

The single figure in the drawing is a side elevational diagrammatic view of apparatus in which the process may be carried out.

Referring more in detail to the drawing, the gas to be treated may be supplied through line 1, controlled by valve 2, tov pump 3 for passage through a heating coil 4. Heating coil 4 may be mounted in a conventional furnace 5 heated by, 110

2 burner 6, the furnace being of any suitable construction to supply the necessary heat to the gases being charged to the system. The heated gases pass from the heating coil 4 through transfer line 7, controlled by valve 8, to point 9, where the heated gas meets the cooling or absorbing medium being supplied through lines 10 or 12. A valve 11 is interposed in line 10 and a valve 12' is interposed in line 12.

As heretofore pointed out, the cooling medium may be introduced into direct or indirect contact with the heated hydrocarbon gas passing through transfer line 7. Preferably, the coooling medium introduced through line 10 is brought into direct physical contact with the highly heated gas, but-it is to be understood that under some conditions it may be desirable to use indirect contact to accomplish the desired cooling.

In either event the cooled gas may pass through cooling coil 13 and to a stabilizer 14 where separation between fixed gas and liquid takes place, the gas passing out through line 15 at the top of the stabilizer, from which line 15 it may be discharged through a valve 16, or a portion may be directed back to the line 1 for reprocessing through a line 18, controlled by valve 17. Cooling means may be provided in the upper portion of the stabilizer 14 which may take the form of a closed coil 19; likewise, heating means may be provided in the lower portion of the stabilizer 14 as indicated by a closed coil 20.

The heating means circulated in coil 20 may be steam, hot oil, or the like, or a portion of the hot material from line '7' may be diverted, as shown, through coil 20 by proper regulation of valves 21 and 22. Liquid collecting in the lower portion of stabilizer 14 may be withdrawn therefrom through line 14', in which line may be interposed a cooler 23, pump 24 and valve 25. By proper manipulation of the valves 25 and 12' regulated portions of the liquid removed from stabilizer 14 may be returned to line 10 for the purpose of assisting in the cooling action, or regulated portions of the cooling or absorbing medium may be supplied through both of the lines 10 and 12.

If desired, a regulated quantity of the liquid passing through valve 25 may be diverted into the cooling coil 19 for cooling purposes.

The apparatus is so designed that it may be operated under a uniform pressure from the inlet of the heating coil to the outlet of the stabilizer, or, for the purpose of making the apparatus more flexible, differential pressures may be employed by proper manipulation of the different valves shown.

While I have shown the use of a cooling coil 13 interposed between line 7 and stabilizer 14, it is to be understood that this cooler may be bypassed and the products of reaction passed directly from line '7' into the stabilizer 14. It is also to be understood that the illustration of the closed coil 19 is purely diagrammatic. In some instances it may be desirable to introduce the cooling medium into direct contact with the gases and vapors in stabilizer 14. This, of course, is within the contemplation of the invention, and I do not wish to limit the invention in any way to the use of an indirect cooling means such as illustrated by closed coil 191' Likewise, it is within the contemplation of the invention that the heating medium passing through closed coil 20 may be introduced into direct physical contact with the liquid collecting in the bottom of the stabilizer 14, and I do not wish to limit myself to the use of an indirect heating medium such as illustrated by closed coil 20.

As an illustrative example of the operation of the present invention, the following may be cited:

Natural gas, for instance, may-be supplied to the apparatus through line 1 and pump 3 to coil 4 where it may be heated to approximately 1400 F. at the coil outlet. An analysis of the gas may show that it contains less than one-tenth of one percent of condensible hydrocarbons. A heavy naphtha of approximately 50 B. gravity may be employed to cool the heated gas to approximately 775 F., after which the cooled mixture may be passed through the cooling coil 13 wherein the temperature is brought down to approximately 150 F. upon entering the'stabilizer. The temperature at the top of the stabilizer may be maintained at approximately 75 F. and the bottom maintained at approximately 190 F. In this illustration it will be assumed that the naphtha was introduced at approximately atmospheric temperature and that it was brought into direct physical contact with the heated products of reaction. The liquid collecting in stabilizer 14 may be withdrawn through line 14 and cooled incooler 23 to approximately 90 F. Analysis of the gas being discharged from the top of the stabilizer through line 15 will show no substantial increase in condensible hydrocarbons in comparison to an analysis of the gas being treated, while the absorbing naphtha will be enriched to the extent of approximately 2 to 2 /2 gallons of liquid per thousand cubic feet of gas being treated and the quality thereof improved to an extent showing the condensibly material absorbed by the naphtha to be at least benzol equivalent.

The relative proportions of cooling liquid to gas will vary, of course, depending upon the conditions of operation and the character and volume of the cooling medium and gas. For most purposes, the proportion of cooling liquid per thousand cubic feet of gas would be approximately five gallons, which will reduce the temperature approximately 400 F.

I claim as my invention:

1. A method of converting hydrocarbon gas into liquefiable aromatic hydrocarbons which comprises subjecting the gas to conversion conditions of temperature and pressure in a heating zone, immediately thereafter checking the conversion reaction by introducing a cool light oil such as naphtha into direct and intimate contact with the heated gas, passing the resultant mixture to a stabilizing zone wherein a temperature gradient is maintained from top to bottom to produce a rectifying effect upon the gases and vapors, separating the condensible from the incondensible reaction products in said zone, and separately withdrawing the gases and liquids fromthe top and bottom respectively of said stabilizing zone. Y

2. A method of converting hydrocarbon gas into liquefiable aromatic hydrocarbons which comprises subjecting the gas to conversion conditions of temperature and pressure in a heating zone, immediately thereafter checking the conversion reaction by introducing a cooling oil into direct and intimate contact with the heated gas,

passing the resultant mixture to a stabilizing zone wherein a temperature gradient is maintained from top to bottom to produce a rectifying effect upon the gasses and vapors, separating the condensible from the incondensible reaction prodfrom top to bottom to produce a, rectifying effect upon the gases and vapors, separating the condensible from the incondensible reaction products in said zone, and separately withdrawing the gases and liquids from the top and bottom respectively of said stabilizing zone, and introducing a portion of the withdrawn liquids into additional quantities of the heated gas issuing from said heating zone to check the conversion reaction thereof.

' GUSTAV EGLOFF. 

